In my prior U.S. Pat. No. 5,007,523, issued Apr. 16, 1991, entitled "Conveyor Belt Scraper Mechanisms", there is disclosed a belt scraper mechanism comprising a cylinder containing a piston slidably movable therein to rotate a belt scraper, via a piston connecting rod, into a scraping position to scrape clean a moving conveyor belt. The belt scraper includes a plurality of resilient belt scraper units which form a continuous scraping edge across substantially the full width of the belt.
By forming one or more of the scraping units adapted to contact center portions of the belt to be of greater hardness than adjacently mounted scraper units adapted to contact side portions of the belt, the substantially continuous scraping edge tends to wear evenly since abrasive material being conveyed usually collects in the center of the belt. Notwithstanding these advantages, there are certain applications where it is desirable to use a scraper element made of a hard, non-resilient material, such as metal, which would be subject to less wear and infrequent replacement relative to the resilient scraper units made of polyurethane as in my aforesaid prior invention.
However, when using a metal scraper element (or a like material which is subject to less wear relative to a polyurethane material as in my prior invention), it is important that the force transmitting mechanism has a shock-absorbing resiliency enabling the scraping edge to be pivoted out of contact with the belt such as when striking a transverse seam or splice connecting adjacent belt portions together. In certain types of conveyor operations, such splices may be formed from a transverse connecting bar which is bolted to overlapping edges of adjacent belt portions by means of nuts and bolts projecting upwardly from the surface of the conveyor belt. The scraping edge contacts such protrusions in a forceful manner (depending upon belt speed) and it is therefore important that the scraping edge has the ability to be pivoted or "rocked" away from the belt surface upon sudden contact with such protrusions without damaging the force transmitting mechanism. While the scraping units of my prior invention have inherent resiliency as a result of the resilient nature of the polyurethane material, such resilient scraper units were subject to premature wear under these types of operating conditions, requiring frequent repair or replacement.
It is accordingly one object of the present invention to provide a shock absorber in a force transmitting mechanism to enable a belt scraper mechanism to absorb incidental shock loading.
My other prior U.S. Pat. No. 5,007,524, issued Apr. 16, 1991, discloses a belt scraper blade wherein a spring clevis interconnects the distal end of a piston connecting rod to the crank extending from the belt scraper mounting shaft to absorb incidental shock loading. However, the use of such an externally mounted spring clevis in the rugged and hostile environment of the conveyor belt results in accumulation of detritus and other scraped material on the spring which may clog the spring and prevent shock-absorbing operations from occurring in a reliable manner. Also, such external placement of the spring tends to result in early wear and fatigue necessitating frequent repair or replacement. Further, the spring often bulged or kinked, preventing reliable operation.
Another object is to provide a shock-absorbing mechanism which is isolated from the external environment and therefore capable of reliable operation in a rugged and hostile environment.
In my prior '524 patent, pressurized water is utilized as a working fluid for applying a force to actuate the belt scraper mechanism to move a piston, slidably contained within a cylinder, interconnected to the belt scraper through the crank. The use of pressurized water minimizes the possibility of explosion or fire. However, water is sometimes unavailable or dangerous for use at below freezing temperatures as often occurs under certain mining operations.
Still another object is to provide a working fluid for actuating a belt scraper mechanism which fluid is normally available at mining sites and under other industrial conditions where materials in granular and pebble like form are often conveyed over long distances from conveyor belts which must be scraped clean.